This invention relates to in-situ solution mining and more particularly to the optimal placement and orientation of the wells comprising a well field for solution mining.
In conventional solution mining practice, a plurality of injection and recovery wells are drilled and completed in a regular repeating fashion. A leach solution is then introduced into the ore body through the injection well and is subsequently recovered by the adjacent recovery or production well. While in contact with the ore body, the leach solution reacts with the mineralization present which may contain uranium and causes selected minerals to become dissolved in the leach solution. The pregnant leach solution is treated above-ground to remove the mineral values therefrom and the leach solution is refortified and recirculated through the ore body.
There are numerous well field patterns that may be utilized in solution mining such as, among others, a 4-spot, 5-spot, or 7-spot pattern. The choice of pattern types may depend upon the permeability of the ore body or the geometric configuration of the ore body. For example, a 4-spot pattern may be more suitable to a highly permeable ore body whereas a 7-spot pattern may be more suitable to a less permeable ore body because the 7-spot pattern has a greater number of injection wells per number of recovery wells for a given cell than does the 4-spot pattern. However, the geometric nature of the 7-spot pattern limits its usefulness in a narrow-winding ore formation due to its repetitive geometric characteristics. Because of these considerations, a 5-spot pattern is the most common cell pattern.
Besides cell pattern, the cell area is an important factor that must be determined in selecting and formulating a well field configuration. The cell area is usually defined to be the area within the perimeter defined by the injection wells surrounding a particular recovery well. There are many techniques for determining the optimum cell area, most of which concern the economics of well field installation and operation. Some of the considerations involved in optimizing cell area are:
(a) mineral concentration per unit area; PA1 (b) cost of installing and completing a well at the depth of mineralization; and PA1 (c) rate of reagent consumption and mineral recovery per well.
With these considerations taken into account, standard optimization techniques can be utilized to determine the optimum cell area for a well field.
Although techniques are available to determine the type of cell pattern and cell area to use with a given ore body or portion of an ore body, the prior art does not describe a method for determining the optimum location of the injection wells relative to the recovery well of a typical cell and their orientation with respect to the ore body. Therefore, what is needed is a method for determining the optimum placement and orientation of a well field pattern for solution mining.